Spring Cloud | 第二篇: 服务消费

 SpringCloud服务间的调用有两种方式：RestTemplate和FeignClient。不管是什么方式，他都是通过REST接口调用服务的http接口，参数和结果默认都是通过json序列化和反序列化。因为Spring MVC的RestController定义的接口，返回的数据都是通过Json序列化成JSON数据。

此文章基于上一篇文章的工程

使用RestTemplate进行服务消费

一：编写服务提供者

我们在Mall_WechatService模块编写服务提供者，有三个mapping分别提供get请求，post请求接收json格式的字符串，post请求接收map格式的数据

@Controller
public class ProduceHelloController {
    private final Logger logger= LoggerFactory.getLogger(this.getClass());

    //get请求
    @ResponseBody
    @RequestMapping("/helloA")
    public String sayHelloA(){
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("name","king james");
        map.put("age",33);
        map.put("team","Cleveland Cavaliers");
        logger.info(JSON.toJSONString(map));
        return JSON.toJSONString(map);
    }

    //POST请求发送json格式的数据
    @ResponseBody
    @RequestMapping("/helloB")
    public String sayHelloB(@RequestBody(required = false)String requestJson){
        try{
            JSONObject jsonObject = JSON.parseObject(requestJson);
            logger.info("helloB"+requestJson);
            return requestJson;
        }
        catch (Exception e){
            logger.info("发生了异常："+e.getMessage());
            return "error";
        }
    }
    //POST请求用Map接收
    @ResponseBody
    @RequestMapping("/helloC")
    public String sayHelloC(@RequestBody Map<String, Object> params){
        try{
            logger.info("helloC"+JSON.toJSONString(params));
            return JSON.toJSONString(params);
        }
        catch (Exception e){
            logger.info("发生了异常："+e.getMessage());
            return "error";
        }
    }
}

二：编写服务消费者

我们在Mall_ManagerService模块编写服务消费者，分别对应上面的三个请求

首先编写RestTemplate的配置

@Configuration
public class ResTemplateConfig {

    @Bean
    //加上这个标签会有负载均衡的效果
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

编写消费的controller

@Controller
public class HelloController {
    private final Logger logger= LoggerFactory.getLogger(this.getClass());

    @Autowired
    private RestTemplate restTemplate;

    String host = "http://mall-wechatservice";//Mall_WechatService模块的spring.application.name

    @ResponseBody
    @RequestMapping("/sayHelloA")
    public String getInfoFromWechatA(){
        String url = host+"/helloA";
        String text = restTemplate.getForObject(url,String.class);
        logger.info("text:"+ text);
        return text;
    }

    @ResponseBody
    @RequestMapping("/sayHelloB")
    public String getInfoFromWechatB(){
        String url = host+"/helloB";
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("name","king james");
        map.put("age",33);
        map.put("team","Cleveland Cavaliers");
        String text = restTemplate.postForObject(url,JSON.toJSONString(map),String.class);
        logger.info("text:"+ text);
        return text;
    }

    @ResponseBody
    @RequestMapping("/sayHelloC")
    public String getInfoFromWechatC(){
        String url = host+"/helloC";
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("name","king james");
        map.put("age",33);
        map.put("team","Cleveland Cavaliers");
        String text = restTemplate.postForObject(url,map,String.class);
        logger.info("text:"+ text);
        return text;
    }
}

我们请求服务消费者的三个URL，然后可以看到Mall_WechatService模块能够正确提供信息并且返回，下面是打印信息

使用Feign进行服务消费

编写服务消费者

首先导入Feign的pom依赖文件，这里一定要注意的是，在SpringCloud最新版本，基于SpringBoot2.0+版本当中，feign的依赖是：

<!--项目使用Feign作为Rest客户端进行远程调用，Spring Cloud版本升级后，Feign依赖变更为:-->
<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

在旧的版本当中，则引入如下依赖：

<!--老版本的springcloud当中的feign依赖-->
<dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-feign</artifactId>
</dependency>

在主类上面加上@EnableFeignClients注解开启Feign的功能

@EnableEurekaClient
@SpringBootApplication
@EnableFeignClients
public class MallManagerServiceApplication {

	public static void main(String[] args) {
		SpringApplication.run(MallManagerServiceApplication.class, args);
	}

}

编写feign接口，调用服务

//括号里面就是你要调用服务的spring.application.name的值
//在这里，我需要去调用mall_wechatservice当中的hello服务
@FeignClient("mall-wechatservice")
public interface HelloServiceRestful {

    /**
     * 请求mall_wechatservice模块的helloA
     * @return
     */
    @RequestMapping("/helloA")
    public String getInfoFromWechatA();
    /**
     * 请求mall_wechatservice模块的helloB
     * @return
     */
    @RequestMapping("/helloB")
    public String getInfoFromWechatB(@RequestBody String json);
    /**
     * 请求mall_wechatservice模块的helloC
     * @return
     */
    @RequestMapping("/helloC")
    public String getInfoFromWechatC(@RequestBody Map<String, Object> params);
}

定义controller，调用服务

@Controller
public class FeignHelloController {

    private final Logger logger= LoggerFactory.getLogger(this.getClass());

    @Autowired
    private HelloServiceRestful helloServiceRestful;

    @ResponseBody
    @RequestMapping("sayFeignHello")
    public String getInfoFromWechat(){
        String text = helloServiceRestful.getInfoFromWechatA();
        logger.info("A"+text);
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("name","king james");
        map.put("age",33);
        map.put("team","Cleveland Cavaliers");
        text = helloServiceRestful.getInfoFromWechatB(JSON.toJSONString(map));
        logger.info("B"+text);
        text = helloServiceRestful.getInfoFromWechatC(map);
        logger.info("C"+text);
        return text;
    }
}

我们输入http://localhost:8011/sayFeignHello，看到控制台打印如下信息，说明服务调用成功